South Yorkshire Coalfield - Geology

Geology

The coal bearing rock strata or coal measures that make up the South Yorkshire Coalfield outcrop in foothills of the Pennines and then dip gently downwards from west to east. This area is known as the exposed coalfield. The coal measures are carboniferous rocks laid down between 290 and 354 million years ago. West of Doncaster the coal measures are overlain by younger rocks, permian limestone, and the area to the east of this is referred to as the concealed coal field.

The northernmost extent of the South Yorkshire Coalfield is marked by the change of the fields richest and highest grade coal seam, the Barnsley Seam or Bed, to a thin seam of inferior coal. This occurs to the north of Barnsley. The southern limit was marked by the Barnsley Bed losing its coking qualities.

The structure of the coal field is not significantly affected by faults except along the River Don between Sheffield and Mexborough. These faults give rise to the Frickley and Maltby troughs where the coal measures are thrown down and lie deeper than other parts of the coalfield.